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c++windowsregistry

RegQueryValueEx returns ERROR_SUCCESS but it does not get me the data buffer. Why?

Following is the code:

#include <windows.h>
#include <iostream>
using namespace std;

#define WIN_32_LEAN_AND_MEAN

void readValueFromRegistry(void)
{
  HKEY hKey;
  DWORD lRv;
  LPCWSTR subKey = L"SYSTEM\\CurrentControlSet\\Services\\HRM";
  lRv = RegOpenKeyEx(
    HKEY_LOCAL_MACHINE,
    subKey,
    0,
    KEY_READ ,
    &hKey
  );

  if (lRv == ERROR_SUCCESS)
  {
    DWORD BufferSize = sizeof(DWORD);
    DWORD dwRet;
    DWORD cbData = 10;
    DWORD lpType;
    wchar_t cbVal[10];
    cout<<"Value before calling RegQueryValueEx is " << cbVal << endl;

    dwRet = RegQueryValueEx(
      hKey,
      L"DataBaseIn",
      NULL,
      &lpType,
      reinterpret_cast<LPBYTE>(cbVal),
      &cbData
    );
    if( lpType == REG_SZ )
        cout << "Reg_SZ" <<endl;
    if( dwRet == ERROR_SUCCESS )
      cout<<"Value is " << cbVal << endl;
    else cout<<"RegQueryValueEx failed " << dwRet << endl;
  }
}

int main()
{
  readValueFromRegistry();
  cin.get();
  return 0;
}

The output is :

Value before calling RegQueryValueEx is 0030F810
Reg_SZ
Value is 0030F810

So RegQueryValueEx returns ERROR_SUCCESS, and returns the type of the value also correctly in the lpType(the Reg_SZ). But I dont get the value in the buffer. It always seems to hold the garbage values. What could be the issue and how to solve?

FYI: The key I am trying to access is created by a windows service developed by me. And DataBaseIn is the value I am trying to access: Some of the values in the HRM key

Solution

  • The char buffer should be initialized not only declared.

    wchar_t cbVal[10] = L"";

    Should use wcout to print unicode strings:

    wcout << cbVal ;